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Indian National Junior Science Olympiad 01/02/2014 1

Homi Bhabha Centre for Science EducationTata Institute of Fundamental Research, Mumbai

Questions (INJSO 2014)

Section A: Questions 1 to 60 are multiple choice with every correct answer carrying 1

mark and every wrong answer carrying -0.25 mark.

SECTION A

Q1. If an axolotl larva of Mexican Salamanderis kept in iodine depleted water; then

a) It will fail to metamorphose but become sexually matureb) There will be no effect on its metamorphosisc) It will metamorphose but remain sexually immatured) It will fail to metamorphose and will remain sexually immature

Q2. Which of the following is an oxidationreduction reaction?

a) H3O+(aq) + CO32-(aq) HCO3-(aq) + H2Ob) HNO3(aq) + NH3(aq) NH4+(aq) + NO3- (aq)c) Mg (s) + F2(g) MgF2(s)d) Pb(NO3)2 (aq) + 2 NaCl (aq) PbCl2(s) + 2NaNO3(aq)

Q3. Which of the following cannot be visible from our moon?

I) Annular eclipse of the Sun.II) Partial eclipse of the Earth.III) Total eclipse of the Sun.

a) I and II b) II and IIIc) I and IV d) Only II

Q4. The immature male germ cells undergo division to produce sperms by the process

of spermatogenesis. Which of the following sentences is correct regarding thisprocess?

a) The primodial germ cells always undergo meiotic division.b) The primodial germ cells divide only by mitotic division.c) Secondary spermatocytes undergo second meiotic division only.d) Spermatozoa are formed from spermatids by meiotic division.

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Q5. Which of the following will change the value of the equilibrium constant for the

reaction?

N2(g) + O2(g) 2NO (g)

a) Add more N2 b) Increase of pressurec) Use a smaller reaction vessel d) Increase the temperature

Q6. Particles P and Q are undergoing uniform horizontal circular motions along

concentric circles of different radii in clockwise sense. P completes each round in 2minutes while Q does it in 5 minutes. Time required by Q to make one revolution

around P is

a) 3 minutes b) 10 minutesc) 10/3 minutes d) This is not possible as Q is moving slower than P.

Q7. Which type of reproduction, from the following, gives evidence that the genetic

information needed for the complete development of an individual is containedactually in a haploid set of chromosomes?

a) Budding in hydrab) Multiple fission in amoebac) Development of male honey bee (Drone) from eggd) Binary fission in paramecium

Q8. The amount of CaCO3which will precipitate if 50ml of 1.0M Na2CO3and 50ml of0.2M CaCl2 are mixed is

a) 5.0 g b) 2.0 gc) 1.0 g d) 0.5 g

Q9. Which of the following statements regarding pollen grain is correct?

a) Tapetum nourishes the developing pollen.b) Sporogenous tissue in the anther is haploidc) Endothesium produces the microspores.d) Only pollen cannot produce a complete plant in any condition.

Q10. Help Sachin to calculate the osmotic pressure of 0.9% aqueous solution of solute X

at 250c. Molar mass of the solute is 60g/mol. ( R= 0.0820 lit-atm K

-1mol

-1)

a) 3.66 x 10-3

atm b) 3.66 atm.

c) 2.44 atm d) 1.63 x 10-3atm

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Q11. Which of the following observations recorded are having FOUR and only FOUR

significant figures?

i) 134.400 m ii) 7680 g

iii) 0.0849 N iv) 2.000 J

a) (i), (iii) and (iv) b) Only (ii)

c) Only (iv) d) (ii) and (iv) only

Q12. A truck and a car moving with the same kinetic energy are brought to rest byapplication of brakes which provide equal total retarding force for both. The truck

has 8 tyres, and weighs 4 times more than the car which has 4 tyres. What can you

say about the distance in which the two vehicles stop?

a) The car will stop at a shorter distance.b) The truck will stop at a shorter distance.c) They will stop at the same distance.d) Not enough information is given.

Q13. Which of the following can be categorized as a parasite in true sense?

a) The female Anopheles mosquito sucks blood from humanb) Human foetus developing in uterus draws nourishment from motherc) Head louse lives on human scalp and lays eggs on hair.d) The cuckoo lays eggs in crows nest for subsequent parental care.

Q14. A human T lymphocyte in the mitotic metaphase stage will contain how many

DNA molecules? (Exclude the DNA of mitochondria)

(a) 23 (b) 46

(c) 184 (d) 92

Q15. In an mRNA the codons are read linearly and each codon consists of threeconsecutive nucleotides which codes for one amino acid. During a deletion

mutation, a deletion of three consecutive bases in the coding region of a gene

cannotresult in one of the following.

a) Deletion of a single amino acid without any other change in the protein.b) Replacement of two adjacent amino acids by a single amino acid.c) Replacement of a single amino acid by another without any other change in

sequence of the protein.

d) Production of a truncated (shorter) protein.

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Q16. Find the number of quanta of radiations of frequency 7.551015

s-1

that must be

absorbed in order to melt 6 g of ice. The approximate energy required to melt 1g of

ice is 333 J. (h=6.6210-34

Js)

a) 0.901022

b) 0.1111020

c) 5.381022

d) 3.991020

Q17. In a certain system of units, force (F), velocity (v) and time (T) are fundamental

quantities and (K) is used for temperature. Dimensions of specific latent heat in

this system are

a) [ v2] b) [ F v T / K ]c) [ F v T ] d) None of the above

Q18. For several days, the temperature at the bottom of a pond is 40

C and the airtemperature just above the top surface of the pond is 10 C. Depth of the pond isL. The Thermal conductivity of ice is 3 times that of water. Thickness of frozenlayer of the ice formed must be

a)3L/4 b) 4L/5c) 3L/5 d) 3L/7

Q19. How much energy in kJ is produced when 7.1 g of gaseous chlorine atoms areconverted to gaseous chloride ions?

(Electron affinity of chlorine is -3.7eV. (1eV/atm = 96.49 kJ/moles)

a) 35.7kJ b) 26.2

kJ

c) 68.5 kJ d) 71.4kJ

Q20. A satellite is launched in a circular orbit of radius R. Another satellite is alsolaunched in an orbit of radius 1.1R. The period of the second satellite is larger than

the first by approximately..

a) 7.5% b) 1.5%

c) 15% d) 10%

Q21. Amol took 10 mL .of 2.2 x 10-5

M hydrochloric acid solution. He then diluted it

to 1 litre. He found that the pH of diluted solution is

a) 4.7 b) 6.7

c) 4.5 d) 6.5

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Q22. The actual path followed by a glucose molecule in the process of aerobicrespiration for production of 36 or 38 ATP would be

a) Cytoplasm ---------- mitochondrial matrix -------- oxysomesb) Cytoplasm ---------------- cytoplasm ------------ F1 particlesc) Mitochondrial matrix -------- F1 particles ---------- oxysomesd) Mitochondrial matrix -------- oxysomes ------------ cytoplasm

Q23. There are 3 containers X, Y and Z. X contains 10ml of water and Z contains 10 ml

of milk. Y contains 5ml of milk (same as in container Z) mixed with 5 ml of

water. All 3 containers have pH value of 6.5. P amount of Acetic acid is added to

container X, Q amount to Y and R amount to Z. Such that the final pH value in

each container is 5.5. Then which of the following is true.

a) P < Q < R b) P < R = Qc) P = Q = R d) P < R < Q

Q24. During fertilization in amphibians, the fusion of egg and sperm plasma is precededby

(P) Release of enzymatic contents from the acrosomal vesicle through exocytosis.

(Q) Binding and interaction of the sperm to vitelline membrane.

(R) Chemo-attraction of the sperm to the egg by soluble factors secreted by egg.

(S) Release of the sperm nucleus into the ooplasm.

Which of the following is the correct sequence?

a) P-Q-S-R b) Q-P-R-S

c) R-P-Q-S d) R-Q-P-S

Q25. A short length linear DNA molecule has 110 thymine and 110 guanine bases. The

total number of nucleotide in the DNA fragment will be

a) 110 b) 880

c) 440 d) 220

Q26. Which of the following solution will form a precipitate with excess 0.1M KOH but

not with excess 0.1M NH3?

a) AgNO3 b) AlCl3c) BaCl2 d) MgCl2

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Q27. Three different circuits (I, II and II) are constructed using identical batteries and

resistors of R and 2R ohm. What can be said about current I in arm AB of each

circuit?

a) II> III> IIII b) II< III< IIIIc) III < II < IIII d) II= III= IIII

Q28. On a summer day one feels very uncomfortable sitting in a room, without an air

conditioner. A bucket of water is kept in the middle of the room for a long time.

Room is thermally insulated from the outside environment.

Which of the following statement is /are correct?

i) If one puts her / his hand in the water, she / he feels water in the bucket to becooler because the water is at a lower temperature than the surrounding.

ii) The quantity of water in the bucket will not change with time.

iii) If ice is brought into the room, the ice begins to melt and the room

temperature begins to fall. The room temperature and the temperature of the

water in the bucket will fall jointly.

iv) Two persons enter the room. Person M is medically normal but person N has

fever with body temperature 104oF. M claims that water kept in a bucket is

warm but N claims that water is cool. Then the water temperature can be

39oC.[ Hint : Boiling point of water at normal pressure is 100

oC = 212

oF.

Freezing point of water at normal pressure is 0 oC = 32oF].

a) ii, iii, and iv b ) iii and iv

c) ii, iii d) only iii

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Q29. An optical system whose cross-section is shown below is constructed from two

different glass isosceles wedges (each with a 30-75-75cross section). The

refractive indices of the two glasses are 1= 3and 2= 2 respectively. A lightbeam is incident at an angle of 60on face AB. The angle of emergence from the

face CD is

a) 0 b) 45c) 15 d) 30

Q30. The given diagram represents a dividing cell stained with giemsa. From the options

given below, identify the correct stage of cell division.

a) Leptotene b) Zygotene

c) Pachytene d) Diakinesis

Q31. The electrolysis of aqueous NaOH solution yields

a) Na at cathode, O2at anode b) H2at cathode, O2at anode

c) H2at anode, O2at cathode d) H2at anode, Na at cathode

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Q35. For a normal unaided eye the least converging power of the eye lens behind the

cornea is 20D and the cornea itself has some converging power. The distance

between the retina and the cornea-eye lens can be approximated to 5/3cm.

Converging power of the cornea is give by:

a)2.5D b) 40Dc)60D d) 19.4D

Q36. Given below are few forces of evolution. Which of the following would be the

best combination of primary forces of evolution?

a) Variation and mutation b) Mutation and isolationc) Variation and migration d) Migration and random genetic drift

Q37. How many molecules of water of hydration are present in 252mg of oxalic acid

( H2C2O4 .2H2O)?

a) 2.68 1018 b) 2.52 10221c) 1.83 10

24d) 2.4 10

21

Q38. Which of the process increases in the absence of light in plants?

a) Rate of uptake of minerals b) Rate of uptake of water

c) Rate of ascent of sap. d) Elongation of internodes

Q39. In the following circuit the ammeter is ideal and reads zero. Value of resistance R

is

a) 500 b) 1000 c) 25000 d) 0.5

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Q44. Variation of the concentration of the reactant (X) and the product (Y) are shown in

the figure. Select the correct statement.

a)

I and II both are kinetic regions.b) I and II both are equilibrium regions.c) I is equilibrium and II is kinetic region.d) I is kinetic and II is equilibrium region.

Q45. A ball falls from rest through air and eventually reaches a constant velocity. For

this fall, force X and Y vary with time as shown.

Which of the following should be force X and Force Y?

Force X Force Y

a) Air Resistance Resultant Forceb) Air Resistance Weightc) Up thrust Resultant Forced) Up thrust Weight

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Q49. Out of the two X chromosomes of human female, one X chromosomes is

inactivated and heterochromatinized. The inactive X-chromosome can be seen as adarkly stained spot and is called as Barr body. Identify the number of Barr bodies

that would be seen in the following genotypes

46 XO 46 XY 46 XXY 46 XXXY

a) 0,1,1,2 b) 0,0,1,2

c) 0,1,2,3 d) 0,0,1,1

Q50. Which of the following is an example of active acquired immunity?

a) Nursing mother transfers some antibodies to infant through colostrum (Breastmilk).

b) Person recovered from measles does not get measles again.c) Injection of antitetanus is given after injury.d) We do not suffer from Distemper, a fatal canine disease.

Q51. The heat of formation of carbon dioxide is X1 and that of water is X2. Anyhydrocarbon on combustion gives carbon dioxide and water. Ethyne is a

hydrocarbon whose formula is C2H2. Heat of combustion of ethyne is X3. Withthe above data predict what will be the heat of formation of ethyne.

a) X1+ X2X3b) 2X1+ X2X3c) 2 X1X2+ X3d) 2X12 X2+ X3

Q52. An overhead crane is being erected to construct a multi storied building. The

horizontal arm of the crane has a linear mass density of 100 kg/m and is 50 m in

length. Its short arm on the opposite side of the support is 5 m long. A pulley

block on the long arm, which can be moved along the arm, weighs 500 kg. Ignore

the mass of the vertical frame. The vertical frame will twist and break if there is

an excess imbalance of more than 10 percent. What is the minimum counter

balance required on the short arm which is to be installed on a permanent basis.

a) 27000 kg b) 29750 kg

c) 26750 kg d) 25000 kg

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Q53. One set of plants was grown at 12 h day and 12 h night period cycles and it

flowered. While for another set of the same plant, the night period wasinterrupted by a flash of light at mid night and it did not flower. The plants used

for the above set of experiments are

a) Long day plant b) Day neutral plant

c) Short day plant d) Darkness neutral plant

Q54. Mayuri was performing thermometric titration and she took 100 ml of 1 M

sulphuric acid and started adding 1M calcium hydroxide and she plotted a graph

of temperature vs volume of the titrant added. In that experiment she found that

temperature was initially increasing and then it started decreasing. The maximum

of the graph is obtained at 100 ml. Calcium hydroxide. What will be the enthalpy

change of this reaction.[ Given H = -13.7 kcal for equivalent.]

a) 13.7 kcal b) 27.4 kcalc) 1.37 kcal d) 2.74 kcal

Q55. BSA was injected into rabbit as antigen and polyclonal antibody was obtained.

From this polyclonal antisera IgG fraction was purified by standard methods. Ifthe same lot of IgG polyclonal antibodies are digested either with Pepsin or

papain and subsequently incubated with the antigen (BSA); find out correct

option from the following.

a) Pepsin digested IgG will precipitate the antigen.b) Papain digested antibody will precipitate the antigen.c) Both the antibody will precipitate antigen.d) None of them will precipitate.

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Q56. Assertion (A): If the volume of the vessel is doubled then for the following

reaction.

A (g) B (g) + C (g)

Equilibrium constant is decreased.Reason (R): Equilibrium constant Kc = X

2/ (1X ) V

a) Both (A) and (R) are true and (R) is the correct explanation of (A).b) Both (A) and (R) are true and (R) is not the correct explanation of (A).c) (A) is true but (R) is false.d) (A) is false but (R) is true.

Q57. Assertion (A): Sodium carbonate can be titrated against sulphuric acid by using

either phenolphthalein or methyl orange as indicator.

Reason (R): The volume of sulphuric acid required to produce colour change fortwo indicators is different. :

a) Both (A) and (R) are true and (R) is the correct explanation of (A).b) Both (A) and (R) are true and (R) is not the correct explanation of (A).c) (A) is true but (R) is false.d) (A) is false but (R) is true.

Q58. is the resultant of and . Their respective magnitudes are C, A and B. Select

correct statement.

a) C may be equal to A.b) C > A and C > B.c) C = A + B.d) C cannot be smaller than of A and B.

Q59. T.H. Morgan discovered that all the genes inDrosophilaare linked to four pairs of

linkage groups which correspond to 4 pairs of chromosomes. Sometimes, the

linkage of some genes, present at some specific distance, is broken and they showindependent assortment. The most plausible reason for brake in the concept of

linkage would be

a) Transposition b) Recombinationc) Translocation d) Sister-chromatid exchange

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Q60. A smooth flat horizontal turntable 4.0 m in diameter is rotating at 0.050 revs per

second. A student at the centre of the turntable, and rotating with it, Places a

smooth flat puck on the turntable 0.50 m from the edge. Which of the following

figures describes the motion of the puck as seen by a stationary observer who isstanding at the side of the turntable and above the turntable?

Section B: Questions 61 to 68 are of 5 marks each. Marks will also be indicated in the

questions if there are more than one part to it.

SECTION B (Long questions)

Q61. Four starts A, B, C, D are in space so that the distances (in light years) betweenthem are given by AB = 6, BC = 8, AC = 10, AD= 8 and CD = 6. Find the

maximum and minimum possible distances between B and D. [5 Marks]

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Q62. In the A, B and O blood grouping system, the blood group O is recessive to Aand B and A and B are co-dominant. Three alleles, namely, IA, IB and IOrepresent the A, B and O system of blood grouping.

Answer the following questions given below.

i. X (Female) is married to Y (Male). They have three children: P (male child), Q(male child) and R (female child). The blood group of X and Y is A and Brespectively. If the blood groups of P and R is B and Q is AB, predict thepossible genotypes for blood groups of all the five members of the family.

[2 Marks]

ii. What will be the possible phenotypes and genotypes of the off-springs if the fatherhas O blood group and the mother has A blood group? [0.5 Marks]

iii. Given below are different blood groups and their genotypes. Find out and write theantigens present on the RBC surface for each blood group (viz: A antigen or Bantigen or nil antigen) and the antibody produced in the serum of each blood group

(viz: anti-A or anti-B or nil antibody) in the table provided below. [2 Marks]

BLOOD GROUP

PHENOTYPE

GENOTYPE ANTIGEN ON THE

SURFACE OF RBC

SERUM ANTIBODY

O I I

A I I or I I

B I I or I I

AB I I

iv. Which combinations of the following blood groups are the universal donors anduniversal recipients respectively? The letter A, B, O represent the blood group and

+ve andve represent the Rh factor. [0.5 Marks]

a) O +ve and AB +veb) O +ve and ABvec) O -ve and AB +ved) O -ve and AB -ve

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Q 63. Observe the Nitrogen cycle given below and answer the following questions.

i. Beginning with free atmospheric nitrogen, arrange the following processes ofnitrogen cycle in proper order. [1 Mark]

a) Ammonificationb) Nitrogen fixationc) Denitrificationd) Nitrification

ii. State whether the following statements are true (T) or false (F). [3 Marks]a) Plants get their nitrogen supply as nitrates and ammonium ions dissolved in

water.

b) Ammonification refers to conversion of free nitrogen to ammonia.c) Nitrogen is fixed only by microorganisms.d)

Rhizobium andAzotobacter are both found in root nodules of leguminous plants.

e) Much of the efforts of nitrogen fixing organisms are neutralized by the action ofdenitrifying bacteria.

f) Volcanic eruption adds free nitrogen to the atmosphere.

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iii. If, in an experiment, all Nitrogenase enzymes in a field are inactivated byirradiation, what will be the immediate vital effect of it? [0.5 Marks]

a) No Fixation of nitrogen in leguminous plants of the field.b) No Fixation of atmospheric nitrogen at all.c) No Conversion of nitrate to nitrite in leguminous plants of the field.d) No Conversion of nitrates to ammonia in soil of the field.

iv. Plants having mutualistic relation with nitrogen fixing bacteria would receivenitrogen in the form of _________ from the bacteria. [0.5 Marks]

a) Ammonium ionsb) Amino acidsc) Nitrates.d) Nitrites

Q64. (10 %) The mass percent of MnO2 in a sample of a mineral is determined byreacting it with a measured excess of As2O3in acid solution, and then titrating the

remaining As2O3 with standard KMnO4. A 0.225 g sample of the mineral is

ground and boiled with 75.0 mL of 0.0125 M As2O3 solution containing 10mL ofconcentrated sulfuric acid. After the reaction is complete, the solution is cooled,

diluted with water, and titrated with 2.25 x10-3

M KMnO4, requiring 16.00ml to

reach the endpoint.

Note: 5 mol of As2O3react with 4mol of MnO4-.

i. Write a balanced equation for the reaction of As2O

3 with MnO

2 in acid

solution. The products are Mn2+and AsO43-. [1Mark]

ii. Calculate the number of moles ofi. As2O3added initially. [1 Mark]

ii. MnO4-used to titrate the excess As2O3. [1 Mark]iii. MnO2in the sample. [1 Mark]

iii. Determine the mass percent of MnO2in the sample. [0.5 Mark]iv. Describe how the endpoint is selected in the KMnO4titration [0.5 Mark]

Q65. A particle is moving on the real line, and its position is observed at four differenttime stamps. At time t = 0, the particle is at x = 0, at time t = 20 seconds, we have

x = 40, at time t = 40 seconds, x = 60 and at time t = 60 seconds, we have x = 90.

Show that at some point of time between 0 and 60 seconds, the acceleration of theparticle was zero. [5 Marks]

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Q66 a. In the Panchatantra stories, one of the popular stories is where a crow sits on a

pot partially filled with water. Crow could not reach up to the water level and sodecides to put in some stones so that the water level rises up to a point from

where crow could drink the water. Let us see if this is possible.

Assume that the container is rectangular in shape with base of 10 cm x 20 cm

and height of 30 cm. Crow has marbles of radius 1 cm to pack the container.

Crow packs the base of the container tightly with a set of marbles. All thesubsequent layers are similar.

i. What should be the initial level of water such that any kind of packing willcertainly bring the water level up to the brim of the container so that it can drinkthe water? [1Marks]

ii. What is the minimum number of marbles required to do the job? [1Marks]Q66 b. Comet ISON, which several astronomy enthusiasts had hoped would be the

'comet of the century', recently disappointed sky observers by breaking apart

before reaching its peak brightness, rendering it too dim to be visible by thenaked eye. In this problem we will consider a simplistic model to try and model

the breakup of the comet.

The breakup of the comet was attributed to the strong effect of tidal forces

acting on the comet due to the sun. These are the same tidal forces that lead to

the commonly observed effect of tides on the earth. Tidal forces are nothing but

a result of the difference of the gravitational attraction at the two ends of the

object.

ISON is made of two identical spheres (m1, m2) attached to each other. As seen

from the sun, one spheres is exactly behind other sphere. Let total mass be mand distance between centers of two spheres be r. Let the distance of closest

approach of the comet from the sun, when it broke, be R. (Distance of closest

approach means, the distance between the comet and the sun, is smallest).

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i. What is the mutual gravitation force by two spheres on each other? [0.25Marks]ii. What gravitation force of sun on closer sphere? [0.25Marks]

iii. By comparing the difference in forces on each of the 2 halves, with respect to themutual force between the two halves, give a relation by governing when the

comet would break up. [1.5Marks]

iv. Convert this relation to find an upper limit on the density of the comet. [1Marks]Q67. The purpose of an airbag is to slow the passengers forward movement into the

steering wheel (or dash board) during a collision and also to provide a cushion

between the passenger and the steering wheel. The goal of an air bag is to help thepassenger come to a stop with minimum damage. One of the ways an air baghelps reduce injury is by spreading the force of impact with the dashboard or

steering wheel over a larger area, as illustrated in Figure 1. When the force is

spread over a larger area of the body, the injuries are less severe.

Figure 1. Force distribution during collision comparing air bag to no air bag.

A certain model of car is equipped with 65.0 liter air bag that inflates to 89.4 m/s in40 milliseconds. The weight of air bag is 2.0 Kg and the thickness of fully inflatedair bag is 30.0 cm.

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One method used to inflate air bags in cars is to use nitrogen produced chemically

from the decomposition of sodium azide:

2NaN3(s) 2Na (s) + 3N2 (g) ---------- (1)

The sodium formed reacts with potassium nitrate to give more nitrogen:

10 Na(s) + 2KNO3(s) K2O(s) + 5Na2O(s) + N2 (g) ----------- (2)

i. Calculate the ratio (by mass) in which the sodium azide and potassium nitrateshould be mixed in order that no metallic sodium remains after the reaction.

[1 Mark]

Na2O and K2O, are highly reactive, so it would be unsafe to allow them to be the

end product of the airbag detonation. These metal oxides react with silicon dioxide(SiO2) in a final reaction to produce silicate glass, which is harmless and stable.

ii. Write the reaction of SiO2with sodium oxide and potassium oxide. [0.5 Mark]

iii. Calculate the total mass of the solid mixture of sodium azide and potassiumnitrate needed to inflate a 72 dm

3air bag is filled with nitrogen gas at of 1 atm and

at room temperature (27oC).

Consider the molar volume of nitrogen gas as 24.0 dm3at 300 K and universal gas

constant, R = 0.0821 liter. atm.mole-1

K-1

(Important: Show all your calculation step clearly) [2 Mark]

The sodium azide is prepared commercially by the reaction between dinitrogenmonoxide and sodium amide.

N2O(g) + 2NaNH2(s) NaN3(s) + NaOH(s) + NH3(g) Hr = 55.8 KJ / mol

iv. Calculate Hr for reaction (1) above, the decomposition of sodium azide.Given:

Compound N2O(g) NaNH2(s) NaOH(s) NH3(g)

Hf(KJ/mol) +82.0 123.7 425.2 -46.1

[1.5 Mark]

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Homi Bhabha Centre for Science Education

Q68. Pradip lives in an apartment on 4th

floor of a 6 story building in Mumbai. It has an

overhead water tank which is just above the 6th

floor. It is kept always full by anautomatic pump. He loves to have bath in hot water at 35

0C, even in summer

even when the outside temperature is 300

C. He uses a 3000 watt instant water

heater for his shower. The hot and cold water taps in his bathroom are similar, andeach can only be in the ON or the OFF state. In the summer he has to open the

cold water tap allowing equal volume of cold water to be mixed with the output of

the heater. As he believes in the water conservation theory of Hugo Chavez,former president of Venezuela, he completes his shower exactly in 3.5 min.

i. Estimate the temperature of the water flowing out of the heater. (Assume no heatis lost when the water flows through the pipe to the shower). [0.5 marks]

ii. What is the rate of flow of water into the water heater fitted on the 4 thfloor of thebuilding? [1 mark]

iii. How much water does Pradip use for every shower? [0.5 marks]iv. In winter the outside temperature is 250C. Keeping the water flow rate into the

heater the same as in the summer, to what extent he should open the cold water

tap (if it is possible to control the flow) to get the same temperature shower as in

the summer? [1 mark]

v. Vinayak lives on the second floor of the same building. Both Vinayak and Pradiphave identical taps and heaters. Assuming all other physical conditions are

identical, if Vinayak maintains the taps open or closed through the yearfollowing the same pattern as Pradip, then what are the temperatures of water

Vinayak receives in the summer and winter? [2 mark]

injso paper 2014

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